Fig. 4

Shake-flask cultivation of K. pneumoniae strain harboring CRISPRi system. a Growth curve of the recombinant K. pneumoniae strain harboring CRISPRi vector and aldehyde dehydrogenase puuC expression vector. b Residual glycerol concentration. c Lactic acid concentration. d Metabolites concentration after 30 h cultivation. 3-HP, 3-hydroxypropionic acid; AC, acetic acid; 1,3-PDO, 1,3-propanediol; 2,3-BDO, 2,3-butanediol. placiL, CRISPRi vector targeting l-lactate dehydrogenase gene pmb; placiD, CRISPRi vector targeting d-lactate dehydrogenase gene ldhA; placiA, CRISPRi vector targeting lactaldehyde dehydrogenase gene aldA; placiM, CRISPRi vector targeting methylglyoxal synthase gene mgsA; placiMALD, CRISPRi vector targeting all above four genes. Kp(ptac-puuC + pdCas9), recombinant K. pneumoniae strain harboring tac promoter-driven puuC expression vector and dCas9 expression vector; Kp(ptac-puuC + placiL), recombinant K. pneumoniae strain harboring puuC expression vector and CRISPRi vector targeting l-lactate dehydrogenase gene pmb; Kp(ptac-puuC + placiD), recombinant K. pneumoniae strain harboring puuC expression vector and CRISPRi vector targeting d-lactate dehydrogenase gene ldhA; Kp(ptac-puuC + placiA), recombinant K. pneumoniae strain harboring puuC expression vector and CRISPRi vector targeting lactaldehyde dehydrogenase gene alhA; Kp(ptac-puuC + placiM), recombinant K. pneumoniae strain carrying puuC expression vector and CRISPRi vector targeting methylglyoxal synthase gene mgsA; Kp(ptac-puuC + placiMALD), recombinant K. pneumoniae strain harboring puuC expression vector and CRISPRi vector simultaneously targeting four genes mgsA, aldA, pmb and ldhA